In the nuclear industry, metal surfaces of various equipment becomes contaminated with radioactive nuclear materials. Exemplary equipment includes piping, valves, gloveboxes, pumps, ventilation, ductwork, machinery and other structural members. The contamination may be fissile nuclear material, uranium plutonium, americium and the like. Specifically, the decontamination of nuclear power plants and weapons facilities of such fissile materials is a difficult problem. There is a tremendous need for improvement in this area, wherein the improvement must combine and meet safety, disposability and cost-effectiveness requirements and minimum halogen impurity levels. Much of the decontamination is highly enriched fissile material particularly uranium-235.
Highly enriched fissile material reacts with neutrons in thermal equilibrium with target nuclei to produce a chain reaction. The chain reaction is sometimes referred to as "criticality". Criticality is achieved when the number of fissioning neutrons equals the number of neutrons leaked out of the geometry and the number of neutrons that undergoes resonant absorbance. During clean-up of equipment, particularly at a weapons facility, great care must be taken to avoid creating conditions which could potentially support achieving criticality.
Conventional techniques for decontaminating other materials including non-fissile radioactive materials often utilize blasting such blasting techniques. See, for example, U.S. Pat. No. 3,895,465 to Korn et al., and U.S. Pat. No. 5,046,289 to Benzel et al. These techniques, however, do not take into account the avoidance of criticality and minimum halogen content material compatibility issues. The inventors are unaware of the use of these known techniques in decontaminating surfaces of fissile or radioactive materials. In fact, many of the techniques may have the potential to enhance the likelihood of achieving criticality, and halogen induced stress cracking corrosion, a very undesirable result.
Thus, there is a need for a media and process for decontaminating surfaces of nuclear and fissile materials that precludes any potential of criticality resulting from fissioning of neutrons and the formation of critical geometry, and also addresses safety disposability, corrosion, and excess radwaste issues.